English

Evaluate ∫-aaf(x)dx, where f(x) = 9x1+9x.

Advertisements
Advertisements

Question

Evaluate `int_-a^a f(x) dx`, where f(x) = `9^x/(1 + 9^x)`.

Sum
Advertisements

Solution

`int_-a^a 9^x/(1 + 9^x)dx`

Let 1 + 9x = u

On differentiating with respect to x.

`\implies` 9x . log 9 = `(du)/dx`

`\implies` 9x dx = `(du)/log9`

= `int_(1 + 9^-a)^(1 + 9^a) (du)/(log9.u)`

= `1/log9 . [log (u)]_(1 + 9^-a)^(1 + 9^a) + C`

= `1/log9 [log (1 + 9^a) - log (1 + 9^-a)] + C`

= `1/log9 [log ((1 + 9^a)/(1 + 9^-a))] + C`.

shaalaa.com
  Is there an error in this question or solution?
2022-2023 (March) Outside Delhi Set 3
Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×